(a) Technical Field
The present disclosure relates to a method of manufacturing carbon fiber reinforced aluminum composites. More particularly, the present disclosure relates to a method that includes a stir casting process during melting and casting processes and reduces a contact angle of carbon against aluminum by inputting carbon fibers while supplying a current to liquid aluminum not only to make the carbon fibers spontaneously and uniformly distributed in the liquid aluminum but to inhibit a formation of an aluminum carbide (Al4C3) phase on an interface of the aluminum and the carbon fiber, thereby manufacturing carbon fiber reinforced aluminum composites having excellent electrical, thermal and mechanical characteristics.
(b) Background Art
Carbon fiber reinforced aluminum composites (hereinafter, “aluminum-carbon fiber composite”) mean a composite material in which carbon fibers are uniformly distributed in aluminum matrix metal as a reinforcing agent. The aluminum-carbon fiber composite has advantages of light weight, high intensity, high stiffness, excellent electric conductivity, excellent thermal conductivity, a small thermal expansion coefficient, excellent wear resistance, and an excellent high temperature property The aluminum-carbon fiber composite has been in the spotlight of industrial fields including structural materials for transportation equipments such as automobiles and aircrafts, machinery industry materials, civil engineering and construction materials, energy field materials, leisure and sports materials, electric and electronic materials, and the like.
Thermal, electrical, and mechanical properties of the aluminum-carbon fiber composite may depend on a technology of uniformly distributing the carbon reinforcing agent in the aluminum matrix metal, a technology of enhancing interfacial bonding strength between aluminum and the carbon fiber, and a technology of preventing an internal defect of the composite. Further, the properties of the aluminum-carbon fiber composite may be influenced by the type, size, shape, and volume fraction of added carbon fibers and a manufacturing process, etc.
A manufacturing process of the aluminum-carbon fiber composite may be generally divided into a solid-phase manufacturing process that use the solid aluminum and a liquid-phase manufacturing process that use the liquid aluminum.
The solid manufacturing process that uses the solid aluminum without melting the aluminum matrix metal may representatively include a powder metallurgy process, a diffusion bonding process, a spray forming process, and the like. The solid-phase manufacturing process can produce a composite whose mechanical properties are superior but the manufacturing cost is high and mass production is difficult, as compared with the liquid-phase manufacturing process.
The liquid-phase manufacturing process using the melted aluminum may representatively include stir casting, compocasting, squeeze casting, infiltration, and the like, and of which the stir casting is the simplest process and the most appropriate for mass production due to the property of being formed in a near-net shape. However, due to the nature of the liquid-phase manufacturing process, a density difference between the aluminum and the carbon fiber is large; carbon fiber are easily tangled because of low wettability by liquid aluminum; a large amount of pores and impurities may be generated during a stirring process; and a brittle Al4C3 phase is easily formed on the interface between the aluminum and the carbon fiber. And as a result, the stir casting is seldom used in manufacturing the aluminum-carbon fiber composite.
As a result, various studies have been conducted in order to improve the wettability of the carbon fiber by the liquid aluminum and inhibit the formation of the aluminum carbide (Al4C3) phase on the interface between the aluminum and the carbon fiber.
A first method is to coat the surface of carbon fiber with metal (Ni, Cu, Ag, Ti, Ta, W, etc.), carbide (SiC, TiC, Pyrolytic carbon, etc.), oxide (Al2O3, TiO2, ZrO2, SiO2, etc.), and boride (TiB2, etc.). However, this additional coating process before manufacturing the composite leads to non-economic feasibility. Furthermore, it is difficult to evenly coat the surface of carbon fibers.
A second method is to input an additive (Mg, Ti, Si, Zr, Cr, Ca, K2ZrF6, K2TiF6, etc.) into a aluminum melt. However, the mechanical properties of the matrix may be changed by the additive.
Therefore, in order to commercialize the aluminum-carbon fiber composite, it is urgent to develop an economical manufacturing process suitable for the mass production, standardize the characteristics of the composite, and ensure reliability.
Accordingly, while the present inventors have studied a mass production method for commercialization of the aluminum-carbon fiber composite, they have applied the stir casting which is the simplest process among the other manufacturing technologies for aluminum-carbon fiber composite and is available in near-net shape forming, and as a result, they have completed the present invention by developing a new liquid-phase manufacturing process capable of solving the problems pointed out in the general stir casting.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.